Make callback on cancel

API.md

@@ -38,15 +38,16 @@ You can also choose one of the following pre-defined filter functions:
 
 ### `select_item.register_on_select_item(callback)`
 Register a call function `callback` to the `select_item` mod.
-Whenever a player selects an item, `callback` is called.
+Whenever a player selects an item or cancels the selection,
+`callback` is called.
 
 #### `callback` function
 This has the function signature `callback(playername, itemstring)`.
 
 * `playername` is the name of the player who selected the item,
-* `itemstring` is the itemstring of the chosen item.
+* `itemstring` is the itemstring of the chosen item or `nil` if aborted
 
-Normally, if the player pushes a button, the formspec is closed.
+Normally, if the player pushes any button, the formspec is closed.
 But if you return `false` in this callback, the formspec is *not*
 Use this when you run into problems.
 

init.lua

@@ -154,7 +154,7 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 				break
 			end
 		end
-		if item then
+		if item or fields.quit then
 			local close = true
 			for i=1,#callbacks do
 				local ret = callbacks[i](playername, item)